U.S. Secretary of State Hillary Clinton says Iran is showing "mounting signs of ruthless repression" in its treatment of opposition activists.

Clinton says Iran's violent crackdown on opposition protests last month, and the arrests of leading reformists are deeply disturbing. She was speaking Monday at a Washington news conference.

Iranian security forces cracked down on major anti-government protests in several cities on December 27, arresting more than 500 demonstrators. Eight people were killed in the unrest. Since then, authorities have detained at least 20 high-profile opposition figures.

Iran's Intelligence Minister Heydar Moslehi says those arrested include foreign nationals suspected of "pursuing psychological warfare." He
said the foreigners were carrying cameras and other equipment. Their nationalities were not disclosed.

Iran's government has repeatedly accused Western media and governments of fomenting the unrest. An Iranian Foreign Ministry spokesman, Ramin Mehmanparast, said Tuesday the detained foreigners will be set free if investigators find them not guilty.